1. Field of the Invention
The present invention relates to a coil antenna including a coil conductor that is arranged around a magnetic core, and to a communication terminal device including the coil antenna.
2. Description of the Related Art
In the above-mentioned type of coil antenna, when a magnetic field generated on the communication partner side interlinks with a coil, an induced electromotive force is generated across the coil. In the above-mentioned type of communication terminal device, data superimposed on the induced electromotive force is reproduced, whereby the data from the communication partner side is received. Furthermore, in the coil antenna, when a current is supplied to flow through the coil, a magnetic field is generated around the coil. The communication terminal device transmits data to the communication partner by employing the generated magnetic field. Hitherto, examples of such coil antenna have been disclosed in Japanese Unexamined Patent Application Publication No. 2003-284476, Japanese Unexamined Patent Application Publication No. 2003-283231 and Japanese Unexamined Patent Application Publication No. 2007-19891.
When trying to reduce the size of the above-described coil antenna, it is conceivable, for example, to narrow a line width of the coil, or to use a material having a high magnetic permeability as a magnetic core. However, if the line width of the coil is narrowed, the influence of a conductor loss would be non-negligible. If the material having a high magnetic permeability is used as the magnetic core, the magnetic field would be confined and therefore a sufficient communication distance could not be ensured.